In the production of hydrocarbons, particularly natural gas, a significant amount of carbon dioxide is also produced from underground formations. The carbon dioxide is separated from the hydrocarbons as part of the refining process. Some of the carbon dioxide is used for other purposes, such as formation fracturing operations and enhanced oil recovery, but the remaining carbon dioxide is disposed of in some fashion. One technique is to inject the carbon dioxide back into an underground formation for permanent storage, known as sequestering. These and other sources of carbon dioxide are also being stored underground to reduce greenhouse gas emissions.
Sequestering carbon dioxide carries a risk that the sequestered carbon dioxide will escape out of the underground formation into other formations, like formations containing drinking water, or escape to the surface. As of the writing of this specification, the inventors are not aware of any sustained instance where sequestered carbon dioxide has escaped to the surface or contaminated a drinking water formation; however, temporary leaks have occurred and any method that could be employed to detect a leak, and stop any such leak, would be beneficial.